Tires are getting old... time to make some decisions (1 Viewer)
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COS80
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- Thread starter
- #62
I went back and found these pictures, which are not conclusive, unfortunately, but help me somewhat. Somebody else showed up right after I started trying to get measurements (the nerve!), so I had to quit before I got any measurements or even a look at the bump stops.
^That's the LF. I was able to deduce, through measuring the real tire and then the picture, that that gap is 1 1/32". I was further able to determine, by comparing specs and measurements on the current tire and the target 315, that with 3/32" treadwear factored in, the new tire would fill 0.614" of that gap. I should be in good shape for this upgrade, assuming I'm on the bump stop (not a safe assumption).
I do intend, of course, to verify this with real measurements, but this bit of trail, the "Shakedown Moguls", is closed until May and the alternative moguls are covered in snow. I'm in no real hurry.
^That's the LF. I was able to deduce, through measuring the real tire and then the picture, that that gap is 1 1/32". I was further able to determine, by comparing specs and measurements on the current tire and the target 315, that with 3/32" treadwear factored in, the new tire would fill 0.614" of that gap. I should be in good shape for this upgrade, assuming I'm on the bump stop (not a safe assumption).
I do intend, of course, to verify this with real measurements, but this bit of trail, the "Shakedown Moguls", is closed until May and the alternative moguls are covered in snow. I'm in no real hurry.
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Box Rocket
SILVER Star
Bumpstops can take a bit of time to get dialed in just right but it isn't too difficult. Having a welder or access to someone that can help with some welding will make it pretty simple. I went with the Timbren bump stops on my 80.
Unfortunately I don't think there is perfect formula for bumpstops since every truck is different because so many variables affect fitment. Most people just follow a basic formula of lift the truck x number of inches, add a bumpstop spacer to factory bumpstops that matches the lift height. Or something close to this, often it seems that most bumpstop spacers are roughly 2" and probably aren't quite right for lifts taller than 2"
This is why it can take some time to figure out the positioning for bumpstops to limit tire/fender contact and more importantly, make sure shocks are protected and won't bottom out before the bumpstop. Another priority for me was to avoid having bumpstops reduce the suspension travel. Many are willing to accept a minor loss of suspension compression to accomplish the other two things I mentioned but I believe its possible to accomplish all three with the understanding that it might also require minor fender trimming to get it perfect.
On my truck I found that the Timbren kits needed a fair amount of adjustment to get them positioned correctly. The rear bumpstop towers that came in the kit were far too tall for my setup. IIRC the tower was 4" tall plus the bumpstop itself. I ended up cutting the towers down to ~2.5" to get the rear bumpstops in the right place for my setup. I found the front bumpstop brackets from Timbren to be too short for what I needed. I ended up adding 1.5" to the height of the brackets to effectively lower the bumpstops to get the right positioning. But remember every setup is slightly different and I did this when fitting 37's so I wouldn't use my specific measurements but the process can be followed to get your own setup where you want it.
You can figure out proper positioning by removing the coil springs and compressing the suspension one corner at a time to find where to position the bumpstops so they protect the shocks and also reduce tire rubbing (making sure to turn the front wheels lock to lock when checking clearance). There is an offroad shop near my house that has a flex ramp outside that I could use to check travel and clearances. That's another option if you have access to a ramp.
As for swaybar disconnects....Lots of differing opinions on the use of swaybars on these trucks. Personally, I'm very much in favor of running front and rear swaybars. The handling characteristics of the trucks with swaybars removed are absolutely horrible and sometimes dangerous especially if you're driving on the highways to get to trails. If it's a trail only rig, then take them off if you like but if the truck is used on the road I think it's important to run the swaybars. In my experience off road, from more overlanding type of trips to much more technical wheeling like tougher trails in Moab or the Rubicon, the rear swaybar has never been a hinderance for suspension travel. In fact, when I was testing for clearances on the flex ramp I also measured suspension travel and the difference between having the swaybars removed completely and with having the rear HD swaybar was less than .5" of distance up the ramp. So I don't think it there is any reason to remove or disconnect the rear swaybar for trail use. The front end can benefit a little more from disconnecting the swaybar. I was able to get a a few inches further up the ramp with the front swaybar removed. Real world experience on trails supports this with improved front end travel on technical trails. So for me, I usually leave the front swaybar connected most of the time but I do run disconnects for wheeling the tougher trails. The LCP front disconnects are affordable and effective. I had some clearance issues with my specific shock setup that prevented me from continuing to use LCP disconnects but I welded my own tabs to the frame for securing the swaybar up and out of the way when disconnected.
I apologize for another long post. But hopefully there is some useful information for someone.
Unfortunately I don't think there is perfect formula for bumpstops since every truck is different because so many variables affect fitment. Most people just follow a basic formula of lift the truck x number of inches, add a bumpstop spacer to factory bumpstops that matches the lift height. Or something close to this, often it seems that most bumpstop spacers are roughly 2" and probably aren't quite right for lifts taller than 2"
This is why it can take some time to figure out the positioning for bumpstops to limit tire/fender contact and more importantly, make sure shocks are protected and won't bottom out before the bumpstop. Another priority for me was to avoid having bumpstops reduce the suspension travel. Many are willing to accept a minor loss of suspension compression to accomplish the other two things I mentioned but I believe its possible to accomplish all three with the understanding that it might also require minor fender trimming to get it perfect.
On my truck I found that the Timbren kits needed a fair amount of adjustment to get them positioned correctly. The rear bumpstop towers that came in the kit were far too tall for my setup. IIRC the tower was 4" tall plus the bumpstop itself. I ended up cutting the towers down to ~2.5" to get the rear bumpstops in the right place for my setup. I found the front bumpstop brackets from Timbren to be too short for what I needed. I ended up adding 1.5" to the height of the brackets to effectively lower the bumpstops to get the right positioning. But remember every setup is slightly different and I did this when fitting 37's so I wouldn't use my specific measurements but the process can be followed to get your own setup where you want it.
You can figure out proper positioning by removing the coil springs and compressing the suspension one corner at a time to find where to position the bumpstops so they protect the shocks and also reduce tire rubbing (making sure to turn the front wheels lock to lock when checking clearance). There is an offroad shop near my house that has a flex ramp outside that I could use to check travel and clearances. That's another option if you have access to a ramp.
As for swaybar disconnects....Lots of differing opinions on the use of swaybars on these trucks. Personally, I'm very much in favor of running front and rear swaybars. The handling characteristics of the trucks with swaybars removed are absolutely horrible and sometimes dangerous especially if you're driving on the highways to get to trails. If it's a trail only rig, then take them off if you like but if the truck is used on the road I think it's important to run the swaybars. In my experience off road, from more overlanding type of trips to much more technical wheeling like tougher trails in Moab or the Rubicon, the rear swaybar has never been a hinderance for suspension travel. In fact, when I was testing for clearances on the flex ramp I also measured suspension travel and the difference between having the swaybars removed completely and with having the rear HD swaybar was less than .5" of distance up the ramp. So I don't think it there is any reason to remove or disconnect the rear swaybar for trail use. The front end can benefit a little more from disconnecting the swaybar. I was able to get a a few inches further up the ramp with the front swaybar removed. Real world experience on trails supports this with improved front end travel on technical trails. So for me, I usually leave the front swaybar connected most of the time but I do run disconnects for wheeling the tougher trails. The LCP front disconnects are affordable and effective. I had some clearance issues with my specific shock setup that prevented me from continuing to use LCP disconnects but I welded my own tabs to the frame for securing the swaybar up and out of the way when disconnected.
I apologize for another long post. But hopefully there is some useful information for someone.
Box Rocket
SILVER Star
Some pics from the described testing.
37’s and bumpstops by Adam Tolman, on Flickr
Bumpstops by Adam Tolman, on FlickrThis pic was with the full height timbren towers in place. Obviously more room for compression was available.
Bumpstop measurements by Adam Tolman, on FlickrSome trail testing. Rear compression is much better here with the bumpstop towers modified. I choose to set the bumpstop where I still have light tire rubbing at full compression. The idea is to maintain as much travel as possible. Also, I figure if the tires aren't rubbing I can fit bigger tires.
Untitled by Adam Tolman, on Flickr
Untitled by Adam Tolman, on Flickr
by Adam Tolman, on FlickrSimilar bumpstop positioning but with 35's. This was using spaced out factory bumpstops. Same suspension setup. The bumpstop positioning here is only about .5" difference from what I ended up at with the Timbrens.
IMG_0630 by Adam Tolman, on Flickr
When I was on 315’s and stock wheels I ran no bump stop extensions in the front and just basic 2” drops in the rear. The front was never a problem. Even with the 2” extensions in the rear the tires would rub a little on the frame and vertical portion of the wheel well. It seems your wheels have 1” negative offset
I agree with the above post in that removing all the springs (did mine 1 axle at a time for safety) and using a floor Jack to push the axle and tire up into a fully compressed position is the only way to come up with what you need for maximum performance out of your bump stops. With 37’s I found that my bump stops had to be tuned to control tire to vehicle interference rather than to protect the shocks. I switched to Timbren bumpstops a couple years ago and like them. For the money they are quite good. I ordered just the bump-stops not the 80 series kit and then made my own mounting set ups to get positioning right where I wanted them. Owning a welder and a few other related tools and knowing how to use them enables us to get exactly what we want and save money doing it.
There are many opinions about what’s a tough trail or what’s a reasonable amount of effort and time expenditure to get from A to B on said trail. Forced induction helps a fat 80 motivate down the smooth roads without the need for super low gearing but it won’t do squat for you on a trail strewn with obstacles that swallow 40” tires. 37’s are just an average size trail rig tire these days. The folks that run those rough and challenging trails dictate the meaning of “reasonable” when it comes to tire size bc their 40”+ tires make the trail what it is. My impression here is that you have a desire to run rougher trails where axles break and dents happen occasionally so I’m still encouraging 37’s, under drive and low range gears, 4.88’s, appropriate armor and the small bits that make it work. I’ve been contemplating 39’s on my current build because there is no substitute for circumference when the terrain is big or the snow is deep…..
I agree with the above post in that removing all the springs (did mine 1 axle at a time for safety) and using a floor Jack to push the axle and tire up into a fully compressed position is the only way to come up with what you need for maximum performance out of your bump stops. With 37’s I found that my bump stops had to be tuned to control tire to vehicle interference rather than to protect the shocks. I switched to Timbren bumpstops a couple years ago and like them. For the money they are quite good. I ordered just the bump-stops not the 80 series kit and then made my own mounting set ups to get positioning right where I wanted them. Owning a welder and a few other related tools and knowing how to use them enables us to get exactly what we want and save money doing it.
There are many opinions about what’s a tough trail or what’s a reasonable amount of effort and time expenditure to get from A to B on said trail. Forced induction helps a fat 80 motivate down the smooth roads without the need for super low gearing but it won’t do squat for you on a trail strewn with obstacles that swallow 40” tires. 37’s are just an average size trail rig tire these days. The folks that run those rough and challenging trails dictate the meaning of “reasonable” when it comes to tire size bc their 40”+ tires make the trail what it is. My impression here is that you have a desire to run rougher trails where axles break and dents happen occasionally so I’m still encouraging 37’s, under drive and low range gears, 4.88’s, appropriate armor and the small bits that make it work. I’ve been contemplating 39’s on my current build because there is no substitute for circumference when the terrain is big or the snow is deep…..
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COS80
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- #66
Since you mention it...
I haven't found a good thread on fender trimming, so if anyone has a link, please drop it in.
These are two excellent ideas. There has to be a ramp around here; I just have to find it.
I have front disconnects. I did not like the on-road handling with the bar removed, but I can feel (and I like) the difference on the trail. Disconnects are the perfect compromise.
Don't apologize, these long, thoughtful posts are gold!
COS80
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- Thread starter
- #67
I'm not set on running all the legendary trails or anything, but I could see that list forming. I'm into this about two years and I know I have a lot to learn. My goal is to minimize my limitations, so when opportunities present themselves, I don't have to shy away. I've already become the guy aiming for the rocks instead of driving around them. I don't see that stopping, so I am inclined to agree with your assessment, only leaving the question of timing. I'm working on that.
Box Rocket
SILVER Star
You'll be fine on 35's for quite a while is my guess. Other than Area BFE in Moab I've run all the tough trails in Moab on 35's with the exception of Pritchett Canyon. There are a few spots where my breakover angle is too low and I would drag the bottom of the truck on 35's. Although I've seen a number of 80s do Pritchett on 35's but it's difficult. Rubicon is doable on 35's. Been through it a few times with 80s on 35's.
As for trimming, it will really come down to where your tires are hitting based on all the variables that have been mentioned. I would plan on removing the factory mudflaps if you haven't already. With 35's I only had minimal trimming of the inside edges of the flares. With 37's there was a bit more trimming of the flares, I rolled the inner fender lip on the rear fenders. In the front I switched the inner fender bolts out for button head screws that would catch on the tires. Moving the front axle forward helped a lot with clearing 37's. I did end up trimming about 2" off the front and rear bumper wings.
COS80
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- Thread starter
- #70
I am absolutely LOVING my new KO3s! Best thing I've done to this truck yet! The grip is astounding, in snow, mud, gravel, loose dirt, everywhere. I made a review thread, of sorts, in the tire/wheel forum.
The downside is it's a real pooch, now, and they hit the fenders. I'll be working on fixing both starting tomorrow.
The downside is it's a real pooch, now, and they hit the fenders. I'll be working on fixing both starting tomorrow.
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Good choice. I almost went with KO3's for the winter grip. I live in WY and drive up a steep snow packed road up to my home for a good part of the year so snow handling was a concern. Ko2s have always performed the best for me on cruisers and trucks I've had and they have a long life span. I've tried duratracs, coopers, hancooks, Falkens, toyo, etc. I'm sure not every one will agree with me, but that's been my experience in this part of the world. They are also pretty quiet on the road.
However, they do run small. So On my 80 I decided to try some Yokohama mud tires and had the center lugs siped. I'm really surprised how well they handle and would do them again. A bit noisier than the K02, but very little slippage on the snow and ice for a mud tire.
Some places old guys spend time getting just the right mow pattern on their lawns, up here we manicure our snow banks. Something special about a long road with clean cut banks, ha ha.
